1. Field of the Invention
The present invention relates generally to power over Ethernet (PoE) and, more particularly, to a system and method for policing bad powered devices in PoE.
2. Introduction
In a PoE application such as that described in the IEEE 802.3af and 802.3 at specifications, a power sourcing equipment (PSE) can deliver power to a powered device (PD) over Ethernet cabling. Various types of PDs exist, including voice over IP (VoIP) phones, wireless LAN access points, Bluetooth access points, network cameras, computing devices, etc.
In accordance with IEEE 802.3af, a PSE can deliver up to 15.4 W of power to a single PD over two wire pairs. In accordance with IEEE 802.3 at, on the other hand, a PSE may be able to deliver up to 30 W of power to a single PD over two wire pairs. Other proprietary solutions can potentially deliver higher or different levels of power to a PD. A PSE may also be configured to deliver power to a PD using four wire pairs.
In the PoE process, a valid device detection is first performed. This detection process identifies whether or not a PSE is connected to a valid PD to ensure that power is not applied to non-PoE capable devices. After a valid PD is discovered, the PSE can optionally perform a power classification. In a conventional 802.3af allocation, each PD would initially be assigned a 15.4 W power classification after a Layer 1 discovery process. An optional classification process could then reclassify the PD to a lower power level. In more complex PoE schemes, a Layer 2 classification engine can be used to reclassify the PD. Layer 2 classification processes can be included in PoE systems such as 802.3af, 802.3 at or proprietary schemes.
PSEs are generally designed to manage a set of subscribing PDs. These PDs can be designed by various manufacturers and can be qualified based on standards of operational performance indicated by a PoE specification. While this qualification ensures that a PD can interoperate with a PSE from another manufacturer, it may not accurately reflect the potential degradation of PD performance over time due to aging of PD components. This degradation in PD performance can have a significant impact on PSE operation. What is needed therefore is a mechanism that enables a PSE to monitor and police PDs to determine when a PD's performance has degraded beyond a certain threshold.